1. Field of the Invention
The invention is directed to a single mode optical waveguide fiber for use in telecommunication systems and more particularly, a waveguide optical fiber allowing parametric amplification within the S-band optical range.
2. Technical Background
The continuous growth of bandwidth requirements in optical based communication systems has resulted in a large demand for systems able to operate within several optical wavelength ranges including the S-band optical range, the C-band optical range and the L-band optical range. The S-band is defined as the wavelengths between 1465 nm and 1525 nm, which lies below the C-band wavelength range which extends between 1525 nm and 1560 nm, which in turn lies just below the L-band wavelength range which extends between 1560 nm and 1600 nm. In order to create a viable operating bandwidth, a large bandwidth must be obtained within each of the operating wavelength ranges. Currently, most telecommunications systems utilize the C-band and L-band signal ranges. Pumping within the S-band optical frequency range has also been utilized to pump Raman amplifiers operating in the C-band range. However, the use of distributed Raman amplification for amplification within the C-band creates a xe2x80x9cdeadxe2x80x9d band between 1491 nm and 1497 nm for the Raman pump.
Parametric amplification is a method previously utilized within the C-band wavelength range to amplify a large bandwidth. Parametric amplification is a non-linear process based on four-wave mixing in high non-linearity dispersion shifted fibers. In short, parametric amplification is a means of amplifying optical waves whereby an intense coherent pump wave is made to interact with a signal wave co-propogating in the nonlinear medium. Four-wave-mixing based on parametric amplification is efficient when phase-matching between the pump signal and the amplified signals is approached. One of the ways to Phase-match the pump and the signals in single mode fibers is to work around the zero point of dispersion in a dispersion shifted fiber.
This invention meets the need for a single mode optical waveguide fiber that allows amplification of an optical signal in the S-band optical range. More specifically, the invention meets the need for a single mode optical waveguide fiber that provides a zero dispersion operating wavelength within the range of between about 1491 nm and about 1497 nm.
In a first embodiment, an optical waveguide fiber, includes a core region having a relative refractive index percent and an inner and an outer radius, and an inner clad layer surrounding and in contact with the core region, the inner clad layer having a refractive index percent and an outer radius. The optical waveguide fiber also includes an outer clad layer surrounding and in contact with the inner clad layer, the outer clad layer having a refractive index. The refractive index and the radii of the core region, the inner clad layer and the outer clad layer are chosen from the following ranges: the index of the core region within the range of from about 1.332 to about 1.628; the index of the inner clad layer within the range of from about 1.301 to about 1.591; the index of the outer clad layer within the range of from about 1.305 to about 1.595; the outer radius of the core region within the range of from about 1.71 xcexcm to about 2.09 xcexcm; and, the outer radius of the inner clad layer within the range of from about 4.41 xcexcm to about 5.39 xcexcm.
In a second embodiment, an optical waveguide fiber includes a core region having a relative refractive index percent and an outer radius, and an inner clad layer surrounding and in contact with the core region, the inner clad layer having a relative refractive index percent and an outer radius. The optical waveguide fiber also includes an outer clad layer surrounding and in contact with the inner clad layer, the outer clad layer having a relative refractive index percent. The refractive index and the radii of the core region, the inner clad layer and the outer clad layer are chosen from the following ranges: the index of the core region within the range of from about 1.338 to about 1.636; the index of the inner clad layer within the range of from about 1.307 to about 1.597; the index of the outer clad layer within the range of from about 1.311 to about 1.603; the outer radius of the core region within the range of from about 2.61 xcexcm to about 3.19 xcexcm; and, the outer radius of the inner clad layer within the range of from about 5.31 xcexcm to about 6.49 xcexcm.
The present invention also includes methods for constructing optical waveguide fibers and an optical communication system employing the fibers in accordance with the embodiments described above.